To enable piezoelectric actuators to be used in applications of automotive technology, building technology and automation technology controllers are needed which can generate voltage-time functions with steep edges and high final voltages at capacitive loads. To achieve a high efficiency switching end stages are used to control these actuators. The discontinuous supply of energy however results in a high level of harmonics and deviation of the actuator deflection from its setpoint function. The advantages of a high level of efficiency, lower rise times and higher final voltages are set against a greater harmonic proportion and deviation from the required value. In particular, when the method is used to control the actuators of a piezo motor, a high proportion of harmonics produces higher noise levels. A potential advantage of the piezoelectric drive, the silent idling, thus remains unused.
Control deviations and harmonics which are caused by discrete energy packets from switched end stages can be reduced by adapting the end stages to the piezo-electric actuators and to the time functions to be achieved.
Limits are imposed on this reduction however by the dynamic range of the circuits and components used, as well as by the effort involved in circuit construction. Thus “charge packets” generated by a switching end step can only be scaled within limits. An end stage with small rise times does not create charge packets of the given small size. A predetermined required value is thus not achieved without a deviation in regulation. Harmonics, created by the clocked operation and the high distortion factor of the generated control function resulting from the control deviations can in fact be attenuated by filtering. However, especially if useful and harmonic frequencies lie close together in the frequency band or if high noise levels are to be attenuated, the outlay involved is extraordinarily high and the efficiency is reduced.